The present invention relates to navigational tools, and in particular, to a mechanical measuring and calculating device usable in navigating aircraft and the like.
One object of the present invention is to provide a flight navigational instrument for measuring linear or curvilinear distances on a map.
Another important object is to provide such a device for determining the flight rate or time of travel represented by known map distances.
It is another object of the present invention to provide a navigational tool which can be operated and read easily.
Yet another object of the invention is to provide such a navigation aid which is simple in construction.
The present device includes an elongate, hollow body having a slot formed along a major portion of its length. Rotatably mounted at one end of the body is a traction element which is engageable with a map surface to produce rotation of the element as the device is moved along a selected path on the map. An indicator mounted for shifting along the slot is operatively connected to the traction element for linear movement in response to rotation of the element. A transparent, cylindrical sleeve is mounted over a portion of the body for rotation relative thereto, this sleeve having radial and axial calibrations by which time or rate of travel determinations can be made.
In operation, the traction element is moved along such path on the map, shifting the indicator to a position along the slot indicating the map distance traversed. The sleeve is then rotated, to align a preselected radial or axial calibration with the slot or the indicator, respectively, whereby time, or rate of travel represented by the measured distance may be determined.
These and other objects and features of the present invention will become more fully apparent when the following description is read in connection with the accompanying drawings, wherein: